This study (1) compares the effectiveness and cost effectiveness of two cystic fibrosis (CF) carrier screening arrangements: a "local" screen, with prescreening education provided by a CF screening pamphlet and a blood sample drawn by a private physician or public health professional; and a genetic center screen, with prescreening education by a genetic counselor and a blood sample drawn by a clinic technician; (2) assesses the effectiveness and cost-effectiveness of a specially developed pregenetic counseling video for CF carrier clients to improve learning in counseling and to increase the utility of counseling information; and (3) conducts a comparison of the sensitivity, specificity, predictive value, and cost-effectiveness of ligase chain reaction (LCR) with polymerase chain reaction (PCR) mutation analysis, including an incremental cost-effectiveness assessment of multiple mutation detection using the GENE SCANNER. To accomplish the first study, 796 close relatives of patients with CF will be randomly assigned to either the "local" or genetic center screens. Before receiving the results of the CF carrier testing and again after receiving carrier status results, subjects will be assessed via telephone interviews, in terms of genetic and medical knowledge, psychological status and selected health behaviors. Cost data will be developed for both CF carrier testing arrangements. To accomplish the second study, all CF carrier genetic counseling clients will be randomly assigned to either (1) view a precounseling video preparing them for the counseling session and identifying the most common difficulties and solutions counseling clients experience in using the information provided in counseling; or (2) receive no special pregenetic counseling preparation. To evaluate the impact of the precounseling video subjects will be interviewed via telephone one, six and twelve months after counseling. Data will be collected on the CF genetic and medical knowledge, psychological status, difficulties in using the information provided in counseling, and selected health behaviors. Cost data will also be collected. To accomplish the third study, LCR and PCR analyses will be performed on all study subjects and the methods compared. Sensitivity, specificity, and predictive values will be computed for each method. Cost information will be compiled on LCR and PCR procedures and analyses, as well as on multiple mutation identification. The proposed studies will provide much needed information on important issues concerning CF carrier screening education, counseling and laboratory methods. By studying the relatives of CF patients, the design constitutes an efficient means of identifying an adequate number of subjects to assure sufficient statistical power. The study employs two randomized controlled trials, permitting strong causal inference regarding the comparative effectiveness of prescreening education procedures and precounseling preparation. Finally, the study compares the accuracy and costs of LCR and PCR mutation analysis as well as the costs of multiple mutation analysis. Combined, such information should be useful in developing more effective and cost effective clinical practice and laboratory methods for CF screening and counseling and for developing public health policy on CF carrier screening programs.